The present invention generally relates to wrenching tools. More specifically, the present invention is directed to a fastener tool assembly for installing and ejecting breakaway torque nuts.
The aerospace industry has made use of “broached-pin” fastening systems for over fifty years. There are many variations, all having in common a method of keeping the bolt or pin from rotating while a nut element is threaded onto it and tightened. Many of the fastening systems used in the aerospace industry are of the frangible fastener type. One such example is the Hi-Lok® fastening system. Such frangible fasteners are used extensively in the aerospace industry due to their simplicity, consistently controlled preload torque and minimum size and weight.
FIGS. 1-4 illustrate a typical frangible fastening system. A bolt 10 is extended through the objects 12 and 14 to be fastened to one another, as illustrated in FIGS. 1 and 2. A threaded portion 16 of the bolt extends beyond the aligned objects 12 and 14. Access to the head 32 of the bolt 10 is usually not possible, and for reasons of weight saving and aerodynamics, the heads 32 of the fasteners are flat so as to be flush with the skin of the aircraft structure, or only protrude slightly. Moreover, these heads 32 do not have any external “hex” or other shape to grip with a wrench to keep the bolt 10 from rotating and turning. Instead, the threaded end 16 of the bolt 10 is provided with an internal hex recess 18 into which a hex-Allen key wrench 20 may be inserted to hold the bolt 10 stationary while an internally threaded nut 22 is fastened thereto.
As illustrated in FIGS. 2 and 3, the operator holds the hex key Allen wrench 20 with one hand, while operating a wrench, typically having a socket 24 at an end thereof, to hold the bolt 10 in place while the nut 22 is fastened onto the threaded portion 16 thereof. Power tools have been developed which incorporate the hex key 20 into the tool. In the same manner, the power tool holds the hex key 20 stationary while the socket 24 is used to thread the nut element 22 onto the threaded end 16 of the bolt 10.
The nut 22 includes a wrenching ring 26 which is configured to engage the socket 24 and an internally threaded collar portion 28. An intermediate neck portion 30 shears the frangible wrenching ring portion 26 from the collar 28 when the applied torque exceeds a predetermined torsional loading, as illustrated in FIG. 4.
The fasteners are applied with one of a variety of wrenching tools which engage the wrenching ring 26 to apply rotational force to the threaded collar 28 and twist the wrenching ring from the threaded collar when the predetermined torsional loading is exceeded. The break-off torque depends on the depth of the groove 30 in the neck which can be selected to meet different torque requirements.
There are typically very strict quality control requirements and measures taken with respect to the installation of breakaway torque nut airframe fasteners. For every breakaway torque nut 22 and bolt 10 used in constructing or repairing the aircraft or other device, a strict accounting of each detached wrenching ring of the breakaway torque nut is required. In some cases, the detached wrenching ring becomes lodged within the open end of the socket used to install the breakaway torque nut 22 to the bolt 10. In this case, the installer must tap the end of the socket 24 containing the wrenching ring 26 to dislodge it from the socket 24. This must be done carefully so that the detached wrenching ring 26 does not become lost. In other instances, the detached wrenching ring 26 easily slips out of and falls away from the socket 24. Of course, this increases the chances that the detached wrenching ring 26 will fall or roll, etc. into an undesirable place or even become lost. In such cases, the installer must cease his or her work and find the lost wrenching ring 26. In some cases, this requires the halting of the manufacturing line until the lost wrenching ring 26 is located and retrieved.
Accordingly, there is a continuing need for a fastener tool assembly for installing and ejecting wrenching rings of breakaway torque nuts. Such an assembly should controllably contain the detached wrenching ring until it is intentionally removed from the assembly. Such an assembly should also permit the installation of several breakaway torque nuts to bolts of the fastener system before requiring that the wrenching rings be removed and collected so as to increase the productivity of the worker. The present invention fulfills these needs, and provides other related advantages.